Process of corrosion inhibition using compounds containing sulfur and amino groups

ABSTRACT

A process for inhibiting the corrosion of ferrous metals in aqueous acidic or briny media comprising the step of adding a composition of the formula   &lt;IMAGE&gt;   where R1 is a hydrocarbon group, O is a pyridine or substituted pyridine, and X is an anion.

This is a division of application Ser. No. 320,048, filed Nov. 10, 1981,now U.S. Pat. No. 4,393,026, issued July 12, 1983, which in turn is adivision of application Ser. No. 161,198, filed June 19, 1980, now U.S.Pat. No. 4,332,967, issued June 1, 1982.

This invention relates to compositions containing both sulfur and aminogroups and to the use thereof as corrosion inhibitors.

The following patents illustrate various patents containing sulfurand/or amino groups which are employed as corrosion inhibitors. Sulfurcontaining, e.g. U.S. Pat. Nos. 3,809,655, 3,759,956, 3,755,176,3,158,476, 2,880,180, 3,404,094, 3,197,403, 3,969,414. Nitrogencontaining, e.g. U.S. Pat. Nos. 3,445,441, 3,450,646; sulfur and aminocontaining, e.g. U.S. Pat. No. 3,414,521.

We have now discovered compositions containing both sulfur and aminogroups, which are useful as corrosion inhibitors. This invention relatesto sulfur-containing corrosion inhibitors which are further enhanced byincluding amino-containing groups in the same molecules; and toamino-containing corrosion inhibitors which are further enhanced byincluding sulfur-containing groups in the same molecule. The presence ofboth sulfur-containing and amino-containing groups synergisticallyenhances the total effect as a corrosion inhibitors.

The sulfur group may be any group effective in inhibiting corrosion,such as the thioether group (--S--), etc.; and the amino group may beany group effective in inhibiting corrosion such as cyclic amidinegroups, for example imidazolenes, tetrahydropyrimidines, etc.,non-cyclic amino groups such as amido amines, quaternary amino-groups,etc., combinations thereof, etc.

In general, the thio group is introduced by any suitable reaction. Onemethod comprises adding a mercaptan across an unsaturated bond ##STR2##R is any group that does not interfere with the addition of themercaptan across the unsaturated group. R may be, for example, ahydrocarbon group such as alkyl, aryl, aralkyl, cycloalkyl, etc.,including substituted derivatives thereof.

The addition of mercaptan to the unsaturated groups can be accomplishedwith or without catalysts. Preferred catalysts include bases such ashydroxides, alkoxides, tertiary amines, etc., or catalysts which cangenerate radicals.

Examples of unsaturated compositions include the following:

1. The acrylate-type compounds, for example the following formula:##STR3## where R is for example hydrogen or an alkyl group, such asmethyl, and R' is hydrogen or an alkyl group, capable of being removedso as to form an amido group, for example methyl, ethyl, propyl,isopropyl, butyl, sec-butyl, tert-butyl, aryl, hexyl, etc. In thepreferred embodiments these compounds are acrylic and methacrylic esterssuch as methyl or ethyl acrylate, methyl or ethyl methacrylate.

2. Acrylonitriles or derivatives thereof such as ##STR4## where R₁ andR₂ are H or hydrocarbon groups such as alkyl, e.g., methyl, ethyl,propyl, butyl, pentyl, etc., for example, methacrylonitrile,ethacrylonitrile, 2-methyl-2-butenenitrile, 2-penetenenitrile.

The following are illustrative.

A. One type of composition involves the reaction of thiols withunsaturated carboxylic acid esters followed by reactions with polyaminesas illustrated by the following equations: ##STR5## R₁ can be anysuitable moiety such as a hydrocarbon or a substituted hydrocarbongroup, for example alkyl, cycloalkyl, aryl, aralkyl, alkaryl, such asmethyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, phenyl,tolyl, etc. The alkyl group may be straight chain or branched. R₂ and R₃can be hydrogen or alkyl such as methyl, ethyl, propyl, etc. butpreferably hydrogen or methyl. R₄ can be any ester moiety such as ahydrocarbon moiety, for example methyl, ethyl, butyl, hexyl, decyl,dodecyl, octadecyl, etc. but preferably methyl or ethyl. R₅ can be H,alkyl, alkanol, aryl, aralkyl, cycloalkyl, ##STR6## where A is alkylenecapable of forming a cyclic amidine ring and R₆ is H or a hydrocarbongroup such as alkyl, etc.

The addition is carried out at any suitable temperature. Temperatures upto the decomposition points of reactants and products such as up to 200°C. or higher have been employed. In practice, one generally carries outthe condensation by heating the reactants below 100° C., such as 80°-90°C. for a suitable period of time, such as a few hours. Where anacrylic-type ester is employed, the progress of the reaction can bejudged by the removal of the alcohol in forming the amide. During theearly part of the reaction alcohol is removed quite readily below 100°C. in the case of low boiling alcohols such as methanol or ethanol. Asthe reaction slows, the temperature is raised to push the condensationto completion and the temperatures may be raised to 150°-200° C. towardthe end of the reaction. Removal of alcohol is a convenient method ofjudging the progress and completion of the reaction which is generallycontinued until no more alcohol is evolved. Based on removal of alcohol,the yields are generally stoichiometric.

The reaction time involved can vary widely depending on a wide varietyof factors. For example, there is a relationship between time andtemperature. In general, lower temperature demands longer times. Inpractice we employ times of from about 2 to 30 hours, such as 5 to 25hours, and preferably 3 to 10 hours.

We have found that although one can employ a solvent, the reaction canbe run without the use of any solvent. In fact, where a high degree ofcross-linking is desired, it is preferable to avoid the use of a solventand most particularly to avoid a polar solvent such as water. However,taking into consideration the effect of solvent on the reaction, wheredesired, any suitable solvent can be employed, whether organic orinorganic, polar or non-polar.

One embodiment relates to compositions where the mole ratios of theunsaturated esters to thiol are greater than 1, such as 2:1, 3:1, 4:1,etc. These products are polymeric aminoamides with attached thio groupsrepresented by the following idealized formula. They are in essence thecomposition of U.S. Pat. No. 3,445,441 modified with thio group.##STR7## These thioethers (1) can be prepared by other methods such as:##STR8## where X is halogen, Cl, Br, I, etc.

B. A second type of composition involves the reaction of thiols withunsaturated nitriles followed by reaction with polyamines. ##STR9## R₃is H, alkyl, aryl, alkaryl, aralkyl, cycloalkyl, alkanol ##STR10## R₄ ishydrocarbon group such as alkyl, etc.

The addition of mercaptan to unsaturated nitrile can be carried out withor without catalyst but it is generally preferred to use a basiccatalyst such as an alkali metal hydroxide, alkoxide or a quarternaryammonium hydroxide.

The cyanoethylated thiol or mixtures of cyanoethylated thiol andcyanoethylated polyamine is reacted with a polyamine under cyclicamidine-forming conditions to form the polymer of this invention.Although the reaction may proceed without a catalyst it is preferablethat a catalyst be employed to speed up the reaction. Among suchcatalysts are organic and inorganic salts such as sulfonic acids, etc.However, it is preferred to use sulfur compounds such as H₂ S,thioacids, thioamides, thioketones, thiourea, dithiobiuret, etc., ascatalysts.

A very useful emobdiment involves the use of a mole ratio of unsaturatednitrile to thiol of greater than 1:1, e.g. 2:1, 3:1, 4:1, etc. Theproduct is a polyamidine modified by thio groupings of the generalidealized formula: ##STR11##

These compositions are in essence the compositions of U.S. Pat. No.3,450,646 modified with thio groups.

C. A third type of composition is derived from thioglycolic acidderivatives and amines according to the formula ##STR12## Thecondensation step can be carried out without or with solvent attemperatures from 60°-200° C. but preferably from 80°-150° C.

The thioglycolic acid derivatives (2) can be prepared by various routessuch as shown in equations (1) and (2): ##STR13## where X is halogen,Cl, Br, I etc. ##STR14## where X is halogen, Cl, Br, I.

D. A fourth type of compositions of this invention involves the reactionof thiols with epichlorohydrin followed by reaction with amines orpolyamines illustrated by the following equation: ##STR15## R₁ is thegroup as defined above. R₂, R₃ and R₄ can be H, alkyl, cycloalkyl, aryl,aralkyl, alkaryl, or alkylamino for polyalkylene such ##STR16##

The reaction step between thiol and epichlorohydrin can be carried outwith or without solvent and with or without catalyst. It is generallypreferred to use a solvent such as an alcohol (e.g. isopropanol,butanol) and a basic catalyst such as a tertiary amine.

The following examples are presented by way of illustration and not oflimitation.

A. Products derived from alkylthiols, unsaturated esters and amines

EXAMPLE 1

In a flask, fitted stirrer, condenser, thermometer, and addition funnelwas placed octyl thiol (36.5 g; 0.25 mole) and Tritton B (5 drops,catalyst) was added. To this thiol, methyl methacrylate (25 g; 0.25mole) was added dropwise while stirring at a rate such that thetemperature was maintained between 50° and 60° C. After stirring for 1hour the addition reaction of the thiol to the methacrylate wascomplete. Infrared analysis showed the absence of thiol SH andunsaturated ester function and presence of saturated ester. (1740 cm⁻¹).To this thiother was added diethylene triamine (26 g; 0.25 mole) and themixture heated to 185°-195° C. As the temperature reached 180° methanolbegan to be liberated and distillation was continued for 1-11/2 hrsduring which time 8 g of distillate was collected (0.25 mole). Theproduct (80 g) was a yellow viscous liquid soluble in aqueous alcoholand water dispersible.

Analysis gave: N, 13.20%; S, 10.15%. (calculated: N, 13.25%; S, 10.09%)

Infrared analysis showed C═O 1650 cm⁻ (amide).

The product has the following structure: ##STR17##

EXAMPLE 2

To dodecylthiol (40 g; 0.2 mole) containing 5 drops of Triton B wasslowly added methyl methacrylate (20 g; 0.2 mole) so that thetemperature was kept below 60° C. After heating for 1 hr. at 50°-60° thereaction between thiol and methacrylate was complete. After cooling toroom temperature diethylene triamine (20 g; 0.2 mole) was added and themixture heated to 180°. Methanol formed in the condensation was allowedto distill from the reaction and was collected (6 g). The product was anamber viscous liquid dispersible in water.

Infrared analysis showed C═O 1650 cm⁻ (amide).

The product has the following structure: ##STR18##

EXAMPLE 3

This example uses the same reactants as Example 1, but in differentratios.

To octyl thiol (14.6 g; 0.1 mole) containing 5 drops of Triton B ascatalyst was added methyl methacrylate (40 g; 0.4 mole) dropwise during45 mins. After stirring for an additional 1 hr. infrared analysis showedthe absence of thiol SH and the presence of both saturated andunsaturated ester groups (1740 cm⁻ and 1725 cm⁻¹). To this mixturediethylene triamine (41.2 g; 0.4 mole) was added and the mixture heatedwith stirring. As the reaction temperature reached 160° methanol wasformed and removed by distillation. After heating at 180°-185° for 1hour 13 g of methanol distillate had been collected leaving 75 g of ayellow viscous product. The product was readily water soluble.

Infrared analysis showed C═O 1650 cm⁻¹ (amide) and no residual estergroups

The product is an oligomeric amino-amide containing thioether groups.

Analysis: Found: N, 20.96; S, 3.97. Calculated: N, 20.24; S, 3.85.

EXAMPLE 4

This example illustrates the use of a different amine.

To octylthiol (30 g; 0.2 mole) containing Triton B (5 drops) as catalystwas added methyl methacrylate (20 g; 0.2 mole dropwise during 1 hour at50°-60°. After stirring 1 hour at 60° aminoethylethanolamine (21 g; 0.2mole) was added and the mixture heated at 170°-185° for 11/2 hrs. Afterthis time distillation of methanol ceased leaving the product as ayellow viscous liquid dispersible in water.

The product is represented by the following structure: ##STR19##

                                      TABLE 1                                     __________________________________________________________________________    Example                                                                            Ester        Thiol     Amine                                             Number                                                                             (moles)      (moles)   (moles)                                           __________________________________________________________________________     5   Methyl methacrylate (0.4)                                                                  Octylthiol (0.2)                                                                        Diethylene Triamine (0.4)                          6   Methyl methacrylate (0.4)                                                                  Octylthiol (0.05)                                                                       Diethylene Triamine (0.4)                          7   Methyl methacrylate (0.2)                                                                  Dodecylthiol (0.1)                                                                      Diethylene Triamine (0.2)                          8   Methyl methacrylate (0.4)                                                                  Dodecylthiol (0.05)                                                                     Diethylene Triamine (0.4)                          9   Methyl methacrylate (0.4)                                                                  Dodecylthiol (0.2)                                                                      Aminoethylethanolamine (0.4)                      10   Methyl methacrylate (0.4)                                                                  Dodecylthiol (0.025)                                                                    Ethylenediamine (0.4)                             11   Methyl Acrylate (0.4)                                                                      Dodecylthiol (0.05)                                                                     Diethylene Triamine (0.4)                         12   Methyl Acrylate (0.4)                                                                      Dodecylthiol (0.025)                                                                    Ethylene diamine (0.4)                            13   Methyl methacrylate (0.25)                                                                 Octylthiol (0.2)                                                                        Ethylene diamine (0.25)                           14   Methyl methacrylate (0.4)                                                                  Octylthiol (0.2)                                                                        Aminoethylethanolamine (0.4)                      15   Methyl Acrylate (0.4)                                                                      Octylthiol (0.05)                                                                       Aminoethylethanolamine (0.4)                      16   Methyl Acrylate (0.4)                                                                      Octylthiol (0.05)                                                                       Diethylene triamine (0.4)                         17   Methyl Acrylate (0.4)                                                                      Octylthiol (0.05)                                                                       Ethylene diamine (0.4)                            __________________________________________________________________________

B. Products derived from alkyl thiols, unsaturated nitrile and amines.

EXAMPLE 18

To octyl thiol (27 g; 0.18 mole) was added acrylonitrile (12 g; 0.23mole) at less than 60° C. After the addition the reaction mixture wasmaintained at 55°-60° for 1 hour. Infrared analysis showed the absenceof thiol-SH and vinyl unsaturation. To this mixture was added diethylenetriamine (24 g; 0.23 mole) and thiourea (1 g) (catalyst). Upon heatingto 125° ammonia evolution commenced and after heating at 165° for 3hours was complete. The product obtained can be represented by thefollowing formula: ##STR20##

EXAMPLE 19

To octyl thiol (64 g; 0.44 mole) containing Triton B (5 drops) wasslowly added acrylonitrile (30 g; 0.57 mole) during 45 mins. at lessthan 60° C. After stirring at ambient temperature for a further 1 houraminoethylethanolamine (60 g; 0.57 mole) and thiourea (1 g) were added.Upon heating to 135° ammonia evolution commenced and became rapid at165°-170°. The ammonia evolution was essentially complete in 3 hoursyielding a dark viscous water dispersible product.

The product is represented by the following formula: ##STR21##

                                      TABLE 2                                     __________________________________________________________________________    Example                                                                            Nitrile   Thiol     Amine                                                Number                                                                             (moles)   (moles)   (moles)                                              __________________________________________________________________________    20   Acrylonitrile (0.4)                                                                     Dodecylthiol (0.2)                                                                      Aminoethylethanolamine (0.4)                         21   Acrylonitrile (0.4)                                                                     Dodecylthiol (0.2)                                                                      Diethylene triamine (0.4)                            22   Acrylonitrile (0.75)                                                                    Dodecylthiol (0.05)                                                                     Ethylene diamine (0.67)                              23   Acrylonitrile (0.4)                                                                     Dodecylthiol (0.05)                                                                     Diethylene triamine (0.4)                            24   Acrylonitrile (0.4)                                                                     Octylthiol (0.27)                                                                       Diethylene triamine (0.4)                            25   Acrylonitrile (0.4)                                                                     Octylthiol (0.05)                                                                       Aminoethylethanolamine (0.4)                         26   Acrylonitrile (0.4)                                                                     Octylthiol (0.05)                                                                       Ethylene diamine (0.4)                               __________________________________________________________________________

C. Products derived from alkylthioacetic acids and amines.

EXAMPLE 27

To decylthioacetic acid (46.4 g; 0.2 mole) in xylene (250 ml) was addedaminoethylethanolamine (20.4 g; 0.2 moles) and the solution heated atreflux for 7 hrs. using a Dean-Stark trap to collect water (7.5 ml).Removal of solvent under vacuum gave the hydroxyethylimidazoline.

The infrared spectrum showed strong C═N absorption at 1590 cm⁻¹.

¹³ C nmr spectrum was also consistent with the structure as shown below:##STR22##

EXAMPLE 28

To tetradecylthioacetic acid (57.6 g; 0.2 mole) in xylene was addedaminoethylethanolamine (20.4 g; 0.2 mole) and the solution heated atreflux with azeotropic removal of water of condensation as in Example27. After removal of solvent under vacuum the product was obtainedshowing a strong infrared absorption at 1590 cm⁻¹ due to imidazoline.The product is represented by the following structure: ##STR23##

EXAMPLE 29

By the procedure of Example 27 octylthioacetic acid was reacted withaminoethylethanolamine to yield the imidazoline represented by thefollowing formula: ##STR24##

D. Products derived from thiols, epichlorohydrin and amines.

EXAMPLE 30

To a solution of octylthiol (38 g; 0.26 mole) in isopropanol (100 ml),containing 2 ml of triethylamine as catalyst, was added epichlorohydrin(24 g; 0.26 mole) dropwise at 60°-40° C. Upon completion of the additionthe mixture was heated at reflux for 2 hours. To this chlorohydrin wasadded a C₁₂ -C₁₄ alkyl dimethylamine (57 g; 0.25 mole) and the mixtureheated at reflux for 12 hrs. The product is represented by the followingformula: ##STR25##

EXAMPLE 31

By a procedure similar to Example 30 octylthiol (38 g; 0.26 mole) inisopropanol (75 ml) was reacted with epichlorohydrin (24 g; 0.26 mole)to yield a chlorohydrin. To this solution was added triethylamine (26 g;0.26 mole) and the mixture heated at reflux for 12 hrs. The product isrepresented by the following formula: ##STR26##

EXAMPLE 32

By the procedure of Example 30 dodecylthiol (53 g; 0.26 mole) inisopropanol (75 ml) was reacted with epichlorohydrin (24 g; 0.26 mole)to yield a chlorohydrin. To the resulting solution was addedtriethylamine (26 g; 0.26 mole) and the mixture heated at reflux for 12hrs. The product obtained is represented by the formula below: ##STR27##

                                      TABLE 3                                     __________________________________________________________________________    Example                                                                            Epichlorohydrin                                                                          Thiol     Amine                                               Number                                                                             (moles)    (moles)   (moles)                                             __________________________________________________________________________    33   Epichlorohydrin (0.2)                                                                    Dodecylthiol (0.05)                                                                     N,N--Dimethylpropylene diamine (0.2)                34   Epichlorohydrin (0.2)                                                                    Dodecylthiol (0.05)                                                                     Ethylene diamine (0.2)                              35   Epichlorohydrin (0.2)                                                                    Dodecylthiol (0.05)                                                                     Diethylene triamine (0.2)                           36   Epichlorohydrin (0.26)                                                                   Octylthiol (0.26)                                                                       Akolidine 11* (0.3)                                 37   Epichlorohydrin (0.07)                                                                   Dodecylthiol (0.07)                                                                     Akolidine 11* (0.1)                                 __________________________________________________________________________     *Akolidine 11 is a crude alkylpyridine mixture manufactured by Lonza.    

Examples of polyamines employed herein are polyalkylene-polyamines, forexample, of the formula ##STR28## where n is an integer 1, 2, 3, 4, 5,6, 7, 8, 9, 10, etc., and A is an alkylene group, provided that thepolyamine contains an alkylene moiety of a cyclic-amidine forming group,i.e., a group having a ##STR29## group.

One or more of the hydrogens on the CH₂ groups may be substituted forexample, by such groups as alkyl groups, for example, methyl, ethyl,etc. Examples of A include ##STR30##

Examples of polyamines include the following ethylene diamine, propylenediamine, diethylene triamine, dipropylene triamine, triethylenetetramine, tripropylene tetramine, tetraethylene pentamine,tetrapropylene pentamine, polyalkyleneimines, i.e. the higher molecularweight amines derived from alkyleneimine such as polyethyleneimines,polypropyleneimines, etc. Mixtures of the above polyamine amines andthose polyamines containing both ethylene and propylene groups, forexample ##STR31## etc., can be employed.

Some of the N-groups may be substituted (provided the polyamine iscyclic-amidine forming), for example, with hydrocarbon groups such asalkyl groups, etc.

In addition, to the basic form of these compositions, one can, incertain instances, prepare salts or quaternaries, either with organic orinorganic acids or quaternizing agents such as benzyl halides, alkylhalides, etc., dihalides such as alkylene dihalide, xylylene dihalides,alkylene ether dihalides such as (XCH₂ CH₂)₂ O, etc. Being basic thecyclic amidine unit readily forms salts, including di- and polysalts.

Examples of acids which can be employed to form salts include HCl, H₂SO₄, H₃ PO₄, hydrocarbon sulfonic acids, acetic acid, oxalic acid,maleic acid, oleic acid, abietic acid, naphthenic acid, rosin, benzoicacid, phthalic acid, diglycollic acid, etc.

In summary, this invention relates to compositions containing bothsulfur and amino groups. Specific compositions thereof are characterizedby the presence of

A. a mercapto or a polymercapto group, and

B. a nitrogen-containing group characterized by at least one of thefollowing:

1. an amido or a polyamido group,

2. a cyclic amidine or a polycyclic amidine group,

3. an epihalohydrin-derived amino-containing group.

Illustrative but non-limiting compositions include the following:##STR32## where R₁ is a hydrocarbon group, such as alkyl, cycloalkyl,aryl, aralkyl, alkaryl, substituted derivatives thereof, etc. R₂, R₃ areH or alkyl, and R₅ is H, alkyl ##STR33## alkanol, etc. where n is 1 ormore, for example, 1 to 10 or more, but preferably 1 to 6. ##STR34##where R₁ is a hydrocarbon group such as alkyl, cycloalkyl, aryl,aralkyl, alkaryl, substituted derivatives thereof, etc., n, m and p areone or more such as where n=1 to 50, but preferably 1 to 10, m=1-10, butpreferably 1 to 6, p=1-50, but preferably 1-20. ##STR35## where R₁ is ahydrocarbon group, such as alkyl, cycloalkyl, aryl, aralkyl, alkaryl,substituted derivatives thereof, etc. R₂ is H or alkyl, and R₃ is H,alkyl, ##STR36## alkanol such as ethanol, etc. where n is one or more,for example, 1-10 or more, but preferably 1 to 6. ##STR37## where R is ahydrocarbon group such as alkyl, cycloalkyl, aryl, aralkyl, alkaryl,substituted derivatives thereof, etc., n and p are one or more, forexample where n=1-10, but preferably 1-5 and p=1-20, but preferably1-10. ##STR38## where R₁ is a hydrocarbon group, such as alkyl,cycloalkyl, aryl, aralkyl, alkaryl substituted derivatives thereof,etc., R₂ is H, alkyl, etc., R₄ is H, alkyl, alkanol such as ethanol,etc., ##STR39## were n is one or more such as 1 to 10, but preferably1-6. ##STR40## were R₁ is a hydrocarbon group, such as alkyl,cycloalkyl, aryl, aralkyl, alkaryl substituted derivatives thereof,etc., and ○N is an amino moiety such as where ##STR41## where R₂, R₃ andR₄, which are the same or different, are H, alkyl, cycloalkyl, aryl,aralkyl, alkaryl, ##STR42## and where n is 1 or more such as 1 to 10,but preferably 1-6. ##STR43## where R=H or alkyl such as methyl, etc.,R'=H or alkanol, such as --CH₂ CH₂ OH, etc., p is one or more such as1-10, but preferably 1-6, n is one or more such as 1-30 but preferably1-17, m is 2-6 preferably 2-3. ##STR44## where R is H or alkyl such asmethyl, etc., and one or more, such as where n=1-30, but preferably1-17, m=1-10, but preferably 1-5, o=2-6, but preferably 2-3, p=1-10, butpreferably 1 to 6, q=1-20, but preferably 1-10. ##STR45## alkanol suchas CH₂ CH₂ OH, etc., where m=1 to 10, but preferably 1 to 6, n=one ormore such as 1 to 30, but preferably 1-17. ##STR46## where n and m areone or more, such as where n=1 to 10, but preferably 1 to 6, and m=1-20,but preferably 1-10. ##STR47## where R is H, alkanol such as CH₂ CH₂ OH,etc., ##STR48## n is one or more such as 1-30, but preferably 1-17, m is1-10 but preferably 1-6. ##STR49## R=alkyl such as methyl, ethyl, etc.,X=anion, such as halogen, for example Cl, Br, I, etc., sulfate,sulfonate, acetate, etc. m and n=one or more, such as 1 to 30, butpreferably 1-17. ##STR50## X=anion such as halogen, for example Cl, Br,I, etc., sulfate, sulfonate, acetate, etc., R=H or alkyl such as methyl,ethyl, etc. n is one or more, such as where n=1-30, but preferably 1 to17, m=2 to 6, but preferably 2 to 3, and p=1 to 10, but preferably 1 to6. ##STR51## φ=pyridine or substituted pyridine, X is anion such ashalogen, for example Cl, Br, I, etc., and sulfate, sulfonate, acetate,etc. n=one or more such as 1-30, but preferably 1-17.

This invention relates to a process of inhibiting corrosion which ischaracterized by treating a metal with the above compositions.

USE AS CORROSION INHIBITORS

This phase of this invention relates to the use of these compositions ininhibiting the corrosion of metals, most particularly iron, steel andferrous alloys. These compositions can be used in a wider variety ofapplications and systems where iron, steel and ferrous alloys areaffected by corrosion. They may be employed for inhibiting corrosion inprocesses which require this protective or passivating coating as bydissolution in the medium which comes in contact with the metal. Theycan be used in preventing atmospheric corrosion, underwater corrosion,corrosion in steam and hot water systems, corrosion in chemicalindustries, underground corrosion, etc.

The corrosion inhibitors contemplated herein find special utility in theprevention of corrosion of pipe or equipment which is in contact with acorrosive oil-containing medium, as, for example, in oil wells producingcorrosive oil or oil-brine mixtures, in refineries, and the like. Theseinhibitors may, however, be used in other systems or applications. Theyappear to possess properties which impart to metals resistance to attackby a variety of corrosive agents, such as brines, weak inorganic acids,organic acids, CO₂, H₂ S, etc.

The method of carrying out this process is relatively simple inprinciple. The corrosion preventive reagent is dissolved in the liquidcorrosive medium in small amounts and is thus kept in contact with themetal surface to be protected. Alternatively, the corrosion inhibitormay be applied first to the metal surface, either as is, or as asolution in some carrier liquid or paste. Continuous application, as inthe corrosive solution, is the preferred method, however.

The present process finds particular utility in the protection of metalequipment of oil and gas wells, especially those containing or producingan acidic constituent such as H₂ S, CO₂, organic acids and the like. Forthe protection of such wells, the reagent, either undiluted or dissolvedin a suitable solvent, is fed down the annulus of the well between thecasing and producing tubing where it becomes commingled with the fluidin the well and is pumped or flowed from the well with these fluids,thus contacting the inner wall of the casing, the outer and inner wallof tubing, and the inner surface of all wellhead fittings, connectionsand flow lines handling the corrosive fluid.

Where the inhibitor composition is a liquid, it is conventionally fedinto the well annulus by means of a motor driven chemical injector pump,or it may be dumped periodically (e.g., once every day or two) into theannulus by means of so-called "boll weevil" device or similararrangement. Where the inhibitor is a solid, it may be dropped into thewell as a solid lump or stick, it may be blown in as a powder with gas,or it may be washed in with a small stream of the well fluids or otherliquid. Where there is gas pressure on the casing, it is necessary, ofcourse, to employ any of these treating methods through a pressureequalizing chamber equipped to allow introduction of reagent into thechamber, equalization of pressure between chamber and casing, and travelof reagent from chamber to well casing.

Occasionally, oil and gas wells are completed in such a manner thatthere is no opening between the annulus and the bottom of the tubing orpump. The results, for example, when the tubing is surrounding at somepoint by a packing held by the casing or earth formation below thecasing. In such wells the reagent may be introduced into the tubingthrough a pressure equalizing vessel, after stopping the flow of fluids.After being so treated, the well should be left closed in for a periodof time sufficient to permit the reagent to drop to the bottom of thewell.

For injection into the well annulus, the corrosion inhibitor is usuallyemployed as a solution in a suitable solvent. The selection of solventwill depend much upon the exact reagent being used and its solubilitycharacteristics.

For treating wells with packed-off tubing, the use of solid "sticks" orplugs of inhibitor is especially convenient. These may be prepared byblending the inhibitor with a mineral wax, asphalt or resin in aproportion sufficient to give a moderately hard and high-melting solidwhich can be handled and fed into the well conveniently.

The protective action of the herein described reagents appears to bemaintained for an appreciable time after treatment ceases, buteventually is lost unless another application is made.

For the protection of gas wells and gas-condensate wells, the amount ofcorrosion inhibitor required will be within range of one-half to 3 lbs.per million cubic feet of gas produced, depending upon the amounts andcomposition of corrosive agents in the gas and the amount of liquidhydrocarbon and water produced. However, in no case does the amount ofinhibitor required appear to be stoichiometrically related to the amountof acids produced by a well, since protection is obtained with much lesscorrosion inhibitor than usually would be required for neutralization ofthe acids produced.

These compositions are particularly effective in the prevention ofcorrosion in systems containing a corrosive aqueous medium, and mostparticularly in systems containing brines.

These compositions can also be used in the prevention of corrosion inthe secondary recovery of petroleum by water flooding and in thedisposal of waste water and brine from oil and gas wells. Still moreparticularly, they can be used in a process of preventing corrosion inwater flooding and in the disposal of waste water and brine from oil andgas wells which is characterized by injecting into a undergroundformulation an aqueous solution containing minor amounts of thecompositions of this invention, in sufficient amounts to prevent thecorrosion of metals employed in such operation.

When an oil well ceases to flow by the natural pressure in the formationand/or substantial quantities of oil can no longer be obtained by theusual pumping methods, various processes are sometimes used for thetreatment of the oil-bearing formation in order to increase the flow ofoil. These processes are usually described as secondary recovyryprocesses. One such process which is used quite frequently is the waterflooding process wherein water is pumped under pressure into what iscalled an "injection well" and oil, along with quantities of water, thathave been displaced from the formation, are pumped out of an adjacentwell usually referred to as a "producing well." The oil which is pumpedfrom the producing well is then separated from the water that has beenpumped from the producing well and the water is pumped to a storagereservoir from which it can again be pumped into the injection well.Supplementary water from other sources may also be used in conjunctionwith the produced water. When the storage reservoir is open to theatmosphere and the oil is subject to aeration this type of waterflooding system is referred to herein as an "open water floodingsystem." If the water is recirculated in a closed system withoutsubstantial aeration, the secondary recovery method is referred toherein as a "closed water flooding system."

Because of the corrosive nature of oil field brines, to economicallyproduce oil by water flooding, it is necessary to prevent or reducecorrosion since corrosion increases the cost thereof by making itnecessary to repair and replace such equipment at frequent intervals.

We have now discovered a method of preventing corrosion in systemscontaining a corrosive aqueous media, and most particularly in systemscontaining brines, which is characterized by employing the compoundsdescribed herein.

We have also discovered an improved process of protecting from corrosionmetallic equipment employed in secondary oil recovery by water floodingsuch as injection wells, transmission lines, filters, meters, storagetanks, and other metallic implements employed therein and particularlythose containing iron, steel, and ferrous alloys, such process beingcharacterized by employing in water flood operation an aqueous solutionof the compositions of this invention.

The invention, then is particularly concerned with preventing corrosionin a water flooding process characterized by the flooding medium,containing an aqueous or an oil field brine solution of thesecompositions.

In many oil fields large volumes of water are produced and must bedisposed of where water flooding operations are not in use or wherewater flooding operations cannot handle the amount of produced water.Most States have laws restricting pollution of streams and land withproduced waters, and oil producers must then find some method ofdisposing of the waste produced salt water. In many instances therefore,the salt water is disposed of by injecting the water into permeable lowpressure strata below the fresh water level. The formation into whichthe water is injected is not the oil producing formation and this typeof disposal is defined as salt water disposal or waste water disposal.The problems of corrosion of equipment are analogous to thoseencountered in the secondary recovery operation by water flooding.

The compositions of this invention can also be used in such waterdisposal wells thus providing a simple and economical method for solvingthe corrosion problems encountered in disposing of unwanted water.

Water flood and waste disposal operations are too well known to requirefurther elaboration. In essence, in the present process, the floodingoperation is effected in the conventional manner except that theflooding medium contains a minor amount of these compositions,sufficient to prevent corrosion.

While the flooding medium employed in accordance with the presentinvention contains water or oil field brine and the compounds of thisinvention, the medium may also contain other materials. For example, theflooding medium may also contain other agents such as surface activeagents or detergents which aid in wetting throughout the system and alsopromote the desorption of residual oil from the formation, sequesteringagents which prevent the deposition of calcium and/or magnesiumcompounds in the interstices of the formation, bactericides whichprevent the formation from becoming plugged through bacterial growth,tracers, etc. Similarly, they may be employed in conjunction with any ofthe operating techniques commonly employed in water flooding and waterdisposal processes, for example five spot flooding, peripheral flooding,etc. and in conjunction with other secondary recovery methods.

The concentration of the corrosion inhibitors of this invention willvary widely depending on the particular composition, the particularsystem, etc. Concentrations of at least about 5 p.p.m., such as about 10to 10,000 p.p.m. for example about 25 to 5,000 p.p.m., advantageouslyabout 50 to 1,000 p.p.m., preferably about 75-250 p.p.m. may beemployed. Larger amounts can also be employed such as 1.5-5.0% althoughthere is generally no commercial advantage in so doing.

For example, since the success of a water flooding operation manifestlydepends upon its total cost being less than the value of the additionaloil recovered from the oil reservoir, it is quite important to use aslittle as possible of these compounds consistent with optimum corrosioninhibition. Since these compounds are themselves inexpensive and areused in low concentrations, they enhance the success of a floodoperation by lowering the cost thereof.

By varying the constituents of the composition, the compounds of thisinvention can be made more oil or more water soluble, depending onwhether the composition is to be employed in oil or water systems.

USE IN ACID SYSTEMS

The compositions of this invention can also be employed as corrosioninhibitors for acid systems, for example as illustrated by the picklingof ferrous metals, the treatment of calcareous earth formations, etc.,as described in the following sections.

USE AS PICKLING INHIBITORS

This phase of the invention relates to pickling. More particularly, theinvention is directed to a pickling composition and to a method ofpicling ferrous metal. The term "ferrous metal" as used herein refers toiron, iron alloys and steel.

To prepare ferrous metal sheet, strip, etc., for subsequent processing,it is frequently desirable to remove oxide coating, formed duringmanufacturing, from the surface. The presence of oxide coating, referredto as "scale" is objectionable when the material is to undergosubsequent processing. Thus, for example, oxide scale must be removedand a clean surface provided if satisfactory results are to be obtainedfrom hot rolled sheet and strip in any operation involving deformationof the product. Similarly, steel prepared for drawing must possess aclean surface and removal of the oxide scale therefrom is essentialsince the scale tends to shorten drawing-die life as well as well asdestroy the surface smoothness of the finished product. Oxide removalfrom sheet or strip is also necessary prior to coating operations topermit proper alloying or adherence of the coating to the ferrous metalstrip or sheet. Prior to cold reduction, it is necessary that the oxideformed during hot rolling be completely removed to preclude surfaceirregularities and enable uniform reduction of the work.

The chemical process used to remove oxide from metal surfaces isreferred to as "pickling." Typical pickling processes involve the use ofaqueous acid solutions, usually inorganic acids, into which the metalarticle is immersed. The acid solution reacts with the oxides to formwater and a salt of the acid. A common problem in this process is"overpickling" which is a condition resulting when the ferrous metalremains in the pickling solution after the oxide scale is removed fromthe surface and the pickling solution reacts with the ferous base metal.An additonal difficulty in pickling results from the liberated hydrogenbeing absorbed by the base metal and causing hydrogen embrittlement. Toovercome the aforementioned problems in pickling, it has been customaryto add corrosion inhibitors to the pickling solution.

The present invention avoids the above-described problems in picklingferrous metal articles and provides a pickling composition whichminimizes corrosion, overpickling and hydrogen embrittlement. Thus thepickling inhibitors described herein not only prevent excessivedissolution of the ferrous base metal but effectively limit the amountof hydrogen absorption thereby during pickling. According to theinvention, a pickling composition for ferrous metal is provided whichcomprises a pickling acid such as sulfuric or hydrochloric acid and asmall but effective amount of the dithiol thione compound of thisinvention, for example at least about 5 p.p.m., such as from about 100to 5,000 p.p.m., but preferably from about 500 to 1,500 p.p.m.

Ferrous metal articles are pickled by contacting the surface (usually byimmersion in the pickling solution) with a pickling composition asdescribed to remove oxide from their surface with minimum dissolutionand hydrogen embrittlement thereof and then washing the ferrous metal toremove the pickling composition thereferom.

USE IN ACIDIZING EARTH FORMATIONS

The compositions of this invention can also be used as corrosioninhibitors in acidizing media employed in the treatment of deep wells toreverse the production of petroleum or gas therefrom and moreparticularly to an improved method of acidizing a calcareous ormagnesium oil-bearing formation.

It is well known that production of petroleum or gas from a limestone,dolomite, or other calcareous-magnesian formation can be stimulated byintroducing an acid into the producing well and forcing it into the oilor gas bearing formation. The treating acid, commonly a mineral acidsuch as HCl, is capable of forming water soluble salts upon contact withthe formation and is effective to increase the permeability thereof andaugment the flow of petroleum to the producing well.

USE AS CORROSION INHIBITORS IN DEEP WELLS

Because of the world wide shortage of pertroleum products, deeper wellsare not being drilled to tap new petroleum fields. However, increaseddepth poses more severe corrosion problems. For example as one drills todepths in excess of 10,000 ft., one encounters temperatures in excess ofabout 200° F., such as from about 200° to 550° , for example from about250° to 500°, but generally within range of about 300° to 450°;pressures in excess of about 5,000 psi, such as from about 5,000 to40,000 for example from about 7,500 to 30,000, but generally in therange of about 8,000 to 20,000; and high acidity, particularly that dueto H₂ S, CO₂, etc., for example H₂ S or CO₂ partial pressures of acidicgases in excess of about 10 psi, such as from about 10 to 20,000, forexample from about 100 to 10,000, but generally from about 200 to 5,000.

These partial pressures of acidic gases can be obtained by analysis ofH₂ S or CO₂ in the range from a few p.p.m. to 80%, for example from1,000 p.p.m. to 50%, but generally from 2% to 40%.

Conditions as extreme as these, place great corrosive stress upon thetubing employed in such wells. Thus, when drilling such wells costs inexcess of $5-$6 million dollars, approximately half of which is tubing,the importance of effective corrosion inhibition is evident. However,when conventional oil well corrosion inhibitors are employed they arefound to be of little or no effectiveness since they tend to degrade,volatilize, polymerize, and either lose effectiveness as corrosioninhibitors or polymerize so as to clog the tubing.

We have further discovered that these compositions are effective ascorrosion inhibitors in systems of high temperature, high pressure andhigh acidity, particularly in deep wells, and most particularly in deepgas wells.

In order to compare the sulfur-amino compositions of this invention withcorresponding non-sulfur amino compositions, the following non-sulfuramino compositions were prepared and tested as corrosion inhibitors.

EXAMPLE 38

To aminoethylethanolamine (52 g; 0.5 mole) was added methyl acrylate (43g; 0.5 mole) dropwise in 30 min. while cooling to maintain a temperaturebelow 50° C. After completing the addition the reaction was heated withstirring to 180°-185°. As the temperature reached 135° methanol began tobe produced and was collected (15 g). Heating was terminated after 4hrs. yielding a viscous product soluble in water.

EXAMPLE 39

By the method of Example 38 methyl acrylate (43 g; 0.5 mole) anddiethylene triamine (52 g; 0.5 mole) was condensed until methanol (15 g) had been collected. The product 77 g was obtained as a viscous darkyellow liquid readily soluble in water.

EXAMPLE 40

Following the procedure of Example 38 methyl methacrylate (50 g; 0.5mole) was reacted with ethylenediamine (60 g; 1.0 mole). After removalof methanol of condensation and some excess ethylene diamine the productwas obtained as a dark viscous oil soluble in water.

EXAMPLE 41

To diethylene triamine (52 g; 0.5 mole) cooled in an ice bath was addedacrylonitrile (30 g; 0.56 mole) in 40 min. at <60° C. Upon completion ofthis addition thiourea (0.8 g) was added as catalyst and the mixtureheated to 150°-165°. Ammonia evolution proceeded rapidly and wascomplete after 4 hours. Upon cooling a viscous brown product wasobtained readily soluble in water.

EXAMPLE 42

Following the procedure of Example 41 aminoethylethanolamine (52 g; 0.5mole) was condensed with acrylonitrile (30 g; 0.56 mole) in presence ofthiourea as catalyst. The viscous product was water soluble.

EXAMPLE 43

Lauric acid (40 g; 0.2 mole) and aminoethylethanolamine (20.1 g; 0.2mole) were heated in xylene (200 ml) in a flask fitted with Dean Starktube. As the solution was heated at reflux water of condensation wascollected. After 12 hrs. 7 ml of water had been collected and thereaction was complete. The product showed infrared absorption consistentwith the imidazoline structure expected as shown below: ##STR52##

CORROSION TEST RESULTS

Corrosion tests were carried out at ambient temperature in 2% sodiumchloride saturated with carbon dioxide. Corrosion rates were measuredusing PAIR meter of the type described in U.S. Pat. No. 3,406,101.Inhibitors were injected after the electrodes had been allowed tocorrode for 2 hours.

Protection is calculated in the usual manner from corrosion rate (R₁) offluids without inhibitor and corrosion rate (R₂) in presence ofparticular inhibitor according to the formula: ##EQU1##

Blank corrosion rates under these conditions was 51 mpy.

                  TABLE 4                                                         ______________________________________                                        Corrosion Test Data                                                                    Percent Protection at Concentration                                  Example    5 ppm   25 ppm     50 ppm                                                                              100 ppm                                   ______________________________________                                        Example 1  --      88         96    --                                        Example 3  --      49         57    87                                        Example 5  --      --         71    92                                        Example 6  --      36         --    74                                        Example 7  61      97         98    99                                        Example 19 --      65         91    96                                        Example 21 --      59         --    90                                        Example 27 --      82         80    --                                        Example 28 --      --         73    --                                        Example 29 --      --         70    --                                        Example 41 --       0          0    --                                        Example 42 --       0         --    --                                        Example 43 --      15         --    --                                        ______________________________________                                    

ACID INHIBITORS TEST IN HYDROCHLORIC ACID

200 ml of 5% hydrochloric acid in a 300 ml beaker is heated to 165°-170°F. and the chemical to be tested is added at the appropriateconcentration. Cleaned 1020 mild steel coupons (7/8×31/4×1/6") areweighed and then placed in the acid for exactly one hour. The couponsare removed and washed with hot water, hot acetone, air dried and thenre-weighed.

Corrosion protection is calculated in the usual manner from the weightloss of the blank (W₁) and weight loss (W₂) in the presence of inhibitoraccording to the formula ##EQU2##

The coupons used in corrosion experiments weighed 20.5-21 g and thetypical weight loss without inhibitors was 1.3 g.

                  TABLE 5                                                         ______________________________________                                        Pickle Acid Inhibitor Tests                                                   Compound    Concentration ppm                                                                           Protection                                          ______________________________________                                        Example 1   250           95%                                                 Example 2   250           95%                                                 Example 5   250           93%                                                 Example 6   250           89%                                                 Example 7   250           95%                                                 Example 8   250           94%                                                 Example 13  250           92%                                                 Example 14  250           92%                                                 Example 19  250           96%                                                 Example 24  250           95%                                                 Example 25  250           76%                                                 Example 26  250           74%                                                 Example 33  250           94%                                                 Example 35  250           92%                                                 Example 36  250           96%                                                 Example 42  250           77%                                                 ______________________________________                                    

We claim:
 1. A process for inhibiting the corrosion of ferrous metals inaqueous acidic or briny media which comprises adding to said media acomposition of the formula ##STR53## where R₁ is a hydrocarbon group, φis a pyridine or substituted pyridine, and X is an anion.
 2. The processof claim 1 wherein the composition has the formula, ##STR54## where φ ispyridine or substituted pyridine, X is an anion, and n is an integer ofone or more.